Checking of duplicate value in JSON object array

Question

I have this json object which has seq 1,2,3,4. And in the main HTML page, user can edit the seq number and I need to make sure that every seq is unique and must not repeat like 2 set of "1" & "1". Unfortunately, it is buggy and sometimes it works sometimes not. Can someone point out my mistake? I want to ignore blank value as well

$scope.myDataset.map(v => v.seq).sort().sort((a, b) => {
    if (a !== '' && b !== '' && a === b) {
        $scope.duplicateFound = true
    }
})

$scope.myDataset = [
    { seq: '1', },
    { seq: '2', },
    { seq: '3', },
    { seq: '4', },
    { seq: '', },
    { seq: '', },

];

`sort` for finding a duplicate? this week the same question arised as well. is there somthing promoting it? — Nina Scholz, Jul 23 '17 at 15:04
Please post your html as well, you could be using an input with type number , which could be mixing with the number chars you have in your json as default. — dev8080, Jul 23 '17 at 15:25

Kermit · Answer 1 · 2017-07-23T15:32:28.310

0

Following code may be helpful for you:

$scope.myDataset = [
    { seq: '1', },
    { seq: '2', },
    { seq: '3', },
    { seq: '4', },
];
var dataSeq = $scope.myDataset.map(v => v.seq);
dataSeq.forEach(function (item, index) {
  if (item !== '' && dataSeq.indexOf(item) !== index ) {
        $scope.duplicateFound = true;
        break;
    }
 })

edited Jul 23 '17 at 15:32

answered Jul 23 '17 at 15:23

Kermit

1,062
6
10

First a traditional sort is carried out, so all duplicates would line up together, so they would be next to each other really. – dev8080 Jul 23 '17 at 15:24
Yes, i'm wrong. – Kermit Jul 23 '17 at 15:30

score 0 · Answer 2 · answered Jul 23 '17 at 15:27

0

Here is a solution using Set and array#some

var myDataset = [
    { seq: '1', },
    { seq: '2', },
    { seq: '3', },
    { seq: '4', },
];

var visited = new Set();
var hasDuplicates = myDataset.some(function(obj) {
    return visited.size === visited.add(obj.seq).size;
});

console.log(Array.from(visited));
console.log(hasDuplicates);

answered Jul 23 '17 at 15:27

Hassan Imam

21,956
5
41
51

I tried to account for null value but it cant work >>>>>>>> return visited.size === visited.add(obj.seq).size && visited.size!=='' && visited.add(obj.seq).size!=='' – user3004237 Jul 23 '17 at 15:47
Do you mean you can have `seq : null`? – Hassan Imam Jul 23 '17 at 15:54
it can be just seq: '' – user3004237 Jul 23 '17 at 16:01
The code will work. You don't have to change anything. – Hassan Imam Jul 23 '17 at 18:35

Nina Scholz · Accepted Answer · 2017-07-23T15:50:17.523

0

You could use an object as hash table and exclude empty strings.

function hasDupes(array) {
    var hash = Object.create(null);
    return array.some(function (a) {
        return a.seq && (hash[a.seq] || !(hash[a.seq] = true));
    });
}

// false
console.log(hasDupes([{ seq: '4' }, { seq: '1' }, { seq: '2' }, { seq: '7' }, { seq: '6' }, { seq: '5' }]));

// false
console.log(hasDupes([{ seq: '' }, { seq: '1' }, { seq: '' }, { seq: '7' }, { seq: '6' }, { seq: '5' }]));

// true
console.log(hasDupes([{ seq: '4' }, { seq: '1' }, { seq: '2' }, { seq: '4' }, { seq: '3' }, { seq: '4' }]));

edited Jul 23 '17 at 15:50

answered Jul 23 '17 at 15:43

Nina Scholz

376,160
25
347
392

i want to ignore empty seq value. only comparing number. – user3004237 Jul 23 '17 at 15:50
@user3004237, it does ignore empty string values. – Nina Scholz Jul 23 '17 at 15:51
How can i turn it into a If statement instead? I tried but got stuck. I dont wanna return true or false – user3004237 Jul 23 '17 at 17:07
`if (hasDupes(array)) { ... }`? – Nina Scholz Jul 23 '17 at 17:09
Solved. Thanks for the help – user3004237 Jul 23 '17 at 17:13

score 0 · Answer 4 · answered Jul 23 '17 at 15:57

0

My guess is you are somehow mixing Strings and integers, which is why your sort is going wrong. I suggest you modify your mapping function a bit.

$scope.myDataset.map(v => parseInt(v.seq + '') ).sort().sort((a, b) => {
    if (a !== '' && b !== '' && a === b) {
        $scope.duplicateFound = true
    }
})

answered Jul 23 '17 at 15:57

dev8080

3,950
1
12
18

nope not really – user3004237 Jul 23 '17 at 16:00
Ok. Would help if you outlined where your code is failing. Theoretically, it seems sound. – dev8080 Jul 23 '17 at 16:01

score 0 · Answer 5 · answered Jul 23 '17 at 16:09

I moved the data object above the iteration. Not sure why you were sorting, what the goal was. I added an extra key value pair to the object that you already have to track if it is visited.

In the loop we add another iteration to compare the next element to the current element of the index. To make sure it doesn't go out of the scope of the array we subtract one from the length and when starting the loop we do 'less than' (<), rather than 'less than or equal'(<=) as this would also cause it to go out of the index range of the array.

The visited key will only be true if it was compared to another iteration after itself.

$scope.duplicateFound = false;
$scope.myDataset = [
            {
                seq: '1',
                visited: false
            },
            {
                seq: '2',
                visited: false
            },
            {
                seq: '3',
                visited: false
            },
            {
                seq: '4',
                visited: false
            },
            {
                seq: '4',
                visited: false,
            }
        ];

        for (var index = 0; index < $scope.myDataset.length - 1; index++){
           var index2 = index + 1;

           if ($scope.myDataset[index]['visited'] === false && $scope.myDataset[index2]['visited'] === false) {
            if ($scope.myDataset[index]['seq'] == $scope.myDataset[index2]['seq']) {
              $scope.duplicateFound = true;
            }
           }

          $scope.myDataset[index]['visited'] = true;
        }

        console.log($scope)

score 0 · Answer 6 · answered Jul 23 '17 at 18:45

if you like to use Lodash (https://lodash.com/docs/4.17.4) JavaScript library then here here is a good solution.

var app = angular.module('test', []);

app.controller('testctrl', function($scope) {

$scope.myDataset = [
{ seq: '1', },
{ seq: '2', },
{ seq: '3', },
{ seq: '4', },
{ seq: '2', },
{ seq: '', },
];

console.log($scope.myDataset);

console.log(_.unionBy(_.filter($scope.myDataset, function(o) {
  return !_.isEmpty(o.seq);
}), 'seq'));

});

Checking of duplicate value in JSON object array

6 Answers6